Discharge of air through the propeller blades of ships is believed to reduce cavitation. In the past, this air has been directed through the propeller shaft to the propeller and out of its blades. In ships having A-bracket supported propeller shafts, a flexible conduit mounted coaxially on the shaft for directing air from the bracket to the propeller is believed desirable.
Such a conduit presents substantial design problems. First, the conduit must be interconnected between a rigid A-bracket and the rotating propeller. Such necessitates a relative rotating seal which is subjected to varying external water pressure and varying air pressure within the conduit. Second, the propeller and its shaft are subject to axial movement of, in some cases, one and one-quarter inches as well as radial movement. Finally, such a conduit should not interfere with sea water lubrication of the A-bracket stave bearings which journal the propeller shaft.